As a related-art bearing device for a wheel, for example, there is proposed a bearing device for a wheel, which is configured so that a hub wheel is separable from an outer joint member of a constant velocity universal joint to attain excellent maintainability (see, for example, Patent Literature 1). As illustrated in FIG. 20, the bearing device for a wheel as disclosed in Patent Literature 1 includes, as main components thereof, a fixed type constant velocity universal joint 106, and a bearing 120 for a wheel including a hub wheel 101, an inner race 102, double-row rolling elements 103 and 104, and an outer race 105.
The hub wheel 101 has an inner raceway surface 107 on an outboard side formed on an outer circumferential surface thereof, and includes a wheel mounting flange 109 for allowing a wheel (not shown) to be mounted thereto. Hub bolts 110 for fixing a wheel disc are equiangularly embedded in the wheel mounting flange 109. The inner race 102 is fitted to a small-diameter step portion 112 formed on an outer circumferential surface of the hub wheel 101 on the inboard side, and an inner raceway surface 108 on the inboard side is formed on an outer circumferential surface of the inner race 102.
The inner race 102 is press-fitted with an adequate interference for the purpose of preventing creep. The inner raceway surface 107 on the outboard side that is formed on the outer circumferential surface of the hub wheel 101 and the inner raceway surface 108 on the inboard side that is formed on the outer circumferential surface of the inner race 102 correspond to double-row inner raceway surfaces. The inner race 102 is press-fitted to the small-diameter step portion 112 of the hub wheel 101, and the end portion of the small-diameter step portion 112 on the inboard side is crimped outward. As a result, the inner race 102 is retained by a crimped portion 111 thus formed and integrated with the hub wheel 101, to thereby apply preload to the bearing 120 for a wheel.
The outer race 105 has double-row outer raceway surfaces 113 and 114 formed on an inner circumferential surface thereof so as to be opposed to the inner raceway surfaces 107 and 108 of the hub wheel 101 and the inner race 102. An outer circumferential surface of the outer race 105 is fitted and fixed to a knuckle extending from a suspension device (not shown) of a vehicle body, and thus the bearing device for a wheel is mounted to the vehicle body.
The bearing 120 for a wheel has a double-row angular contact ball bearing structure. Specifically, the rolling elements 103 and 104 are interposed between the inner raceway surfaces 107 and 108 formed on the outer circumferential surfaces of the hub wheel 101 and the inner race 102 and the outer raceway surfaces 113 and 114 formed on the inner circumferential surface of the outer race 105, and the rolling elements 103 and 104 in the respective rows are equiangularly supported by retainers 115 and 116.
In opening portions of the bearing 120 for a wheel at both ends thereof, a pair of seals 117 and 118 for sealing annular spaces between the outer race 105 and the hub wheel 101 and between the outer race 105 and the inner race 102 so as to be held in sliding-contact with the outer circumferential surfaces of the hub wheel 101 and the inner race 102 is fitted to a radially inner part of the outer race 105 at both end portions thereof. The seals 117 and 118 prevent leakage of grease filled inside and entry of water and foreign matter from the outside.
The constant velocity universal joint 106 includes an outer joint member 124 being arranged at one end of an intermediate shaft 122 serving as a drive shaft 121 and having track grooves 123 formed in an inner circumferential surface thereof, an inner joint member 126 having track grooves 125 formed in an outer circumferential surface thereof so as to be opposed to the track grooves 123 of the outer joint member 124, balls 127 assembled into spaces between the track grooves 123 of the outer joint member 124 and the track grooves 125 of the inner joint member 126, and a cage 128 interposed between the inner circumferential surface of the outer joint member 124 and the outer circumferential surface of the inner joint member 126 so as to retain the balls 127.
The outer joint member 124 includes a mouth section 129 for accommodating internal components such as the inner joint member 126, the balls 127, and the cage 128, and a stem section 130 integrally extending from the mouth section 129 in an axial direction. An axial end of the intermediate shaft 122 is press-fitted to the inner joint member 126, and is coupled by spline fitting so as to allow torque transmission therebetween.
A bellows-like boot 131 made of a resin is mounted between the outer joint member 124 of the constant velocity universal joint 106 and the intermediate shaft 122 so as to prevent leakage of a lubricant such as grease filled inside the joint, and to prevent entry of foreign matter from outside the joint, thereby attaining a structure of closing an opening portion of the outer joint member 124 with the boot 131.
The boot 131 includes a large-diameter end portion 133 fixed to an outer circumferential surface of the outer joint member 124 by fastening with a boot band 132, a small-diameter end portion 135 fixed to an outer circumferential surface of the intermediate shaft 122 by fastening with a boot band 134, and a flexible bellows portion 136 connecting the large-diameter end portion 133 and the small-diameter end portion 135 and being reduced in diameter in a range of from the large-diameter end portion 133 toward the small-diameter end portion 135.
FIG. 21 illustrates a state before press-fitting the stem section 130 of the outer joint member 124 to a shaft hole 138 of the hub wheel 101. As illustrated in FIG. 21, a male spline including a plurality of convex portions 137 extending in the axial direction is formed on an outer circumferential surface of the stem section 130 of the outer joint member 124. On the other hand, a simple cylindrical portion 139 having no female spline formed thereon is formed on an inner circumferential surface of the shaft hole 138 of the hub wheel 101.
FIG. 22 illustrates a state after press-fitting the stem section 130 of the outer joint member 124 to the shaft hole 138 of the hub wheel 101. The stem section 130 of the outer joint member 124 is press-fitted to the shaft hole 138 of the hub wheel 101, and the shape of each convex portion 137 of the stem section 130 is transferred to the inner circumferential surface of the shaft hole 138 of the hub wheel 101. Thus, as illustrated in FIG. 22, concave portions 140 brought into close contact with the corresponding convex portions 137 with interferences therebetween are formed on the inner circumferential surface of the shaft hole 138 of the hub wheel 101, to thereby define a convex and concave fitting structure in which the convex portions 137 and the concave portions 140 are brought into close contact with each other at an entire fitting contact portion therebetween. As a result, the outer joint member 124 and the hub wheel 101 are coupled to each other so as to allow torque transmission therebetween.
As described above, under the state in which the stem section 130 of the outer joint member 124 is press-fitted to the shaft hole 138 of the hub wheel 101, as illustrated in FIG. 20, a bolt 142 is threadedly engaged with a female thread 141 formed at an axial end of the stem section 130 of the outer joint member 124, and is fastened in a state of being locked on an end surface of the hub wheel 101, to thereby fix the constant velocity universal joint 106 to the hub wheel 101.